Arterial Levels of Oxygen Stimulate Intimal Hyperplasia in Human Saphenous Veins via a ROS-Dependent Mechanism

Abstract

Saphenous veins used as arterial grafts are exposed to arterial levels of oxygen partial pressure (pO2), which are much greater than what they experience in their native environment. The object of this study is to determine the impact of exposing human saphenous veins to arterial pO2. Saphenous veins and left internal mammary arteries from consenting patients undergoing coronary artery bypass grafting were cultured ex vivo for 2 weeks in the presence of arterial or venous pO2 using an established organ culture model. Saphenous veins cultured with arterial pO2 developed intimal hyperplasia as evidenced by 2.8-fold greater intimal area and 5.8-fold increase in cell proliferation compared to those freshly isolated. Saphenous veins cultured at venous pO2 or internal mammary arteries cultured at arterial pO2 did not develop intimal hyperplasia. Intimal hyperplasia was accompanied by two markers of elevated reactive oxygen species (ROS): increased dihydroethidium associated fluorescence (4-fold, p<0.05) and increased levels of the lipid peroxidation product, 4-hydroxynonenal (10-fold, p<0.05). A functional role of the increased ROS saphenous veins exposed to arterial pO2 is suggested by the observation that chronic exposure to tiron, a ROS scavenger, during the two-week culture period, blocked intimal hyperplasia. Electron paramagnetic resonance based oximetry revealed that the pO2 in the wall of the vessel tracked that of the atmosphere with a ~30 mmHg offset, thus the cells in the vessel wall were directly exposed to variations in pO2. Monolayer cultures of smooth muscle cells isolated from saphenous veins exhibited increased proliferation when exposed to arterial pO2 relative to those cultured at venous pO2. This increased proliferation was blocked by tiron. Taken together, these data suggest that exposure of human SV to arterial pO2 stimulates IH via a ROS-dependent pathway.

Upregulation of miR-126-3p promotes human saphenous vein endothelial cell proliferation in vitro and prevents vein graft neointimal formation ex vivo and in vivo

“…HSVECs were maintained in ECM medium supplemented with 25 ml of fetal bovine serum (FBS), 5 ml of endothelial cell growth supplement and 5 ml of penicillin/streptomycin solution. HSVSMCs were obtained by the explant method as previously described [ 53 ]. The VSMC phenotype was confirmed by the typical “hill and valley” growth pattern in culture and by immunofluorescence staining using antibodies against α-smooth-muscle actin (α-SMA).…”

Attenuation of the in vitro neurotoxicity of 316L SS by graphene oxide surface coating

“…In order to establish GO’s role in modulating inflammatory responses if any, reactive oxygen species (ROS) expression in SHSY-5Y cells cultured atop GO-coated meshes was analyzed using immunofluorescence following published procedures (65). Levels of ROS in SHSY-5Y cultured in the vicinity of GO-coated surfaces were assessed using conversion of non-fluorescent dihydroethidium (DHE:Sigma) to fluorescent ethidium bromide.…”

Vasa vasorum inside out/outside in communication: a potential role in the patency of saphenous vein coronary artery bypass grafts

“…For instance, it is suggested that stripping of varicose hSV reduces local production of harmful reactive oxygen metabolites (ROM) resulting in a positive effect on vein physiology (Flore et al 2003 ). Furthermore, according to Joddar et al ( 2015 ), the higher arterial levels of oxygen and elevated level of reactive oxygen species (ROS) stimulates intimal hyperplasia in hSV organ culture models where the hSVs were harvested by standard endovascular techniques. However, data from such in vitro organ culture studies (14 days in the medium, changed every 2 days; some culture medium also containing compound tiron to help reoxygenation) may be limited and may not reflect the true physiological events that occur in vivo hSV when used in CABG patients.…”